UV to Mid-IR SEDs of Low Redshift Quasars Zhaohui Shang (Tianjin Normal University/University of Wyoming) Michael Brotherton, Danny Dale (University of Wyoming) Dean Hines (Space Science Institute) Xi’an Oct. 20, 2006

Quasar Spectral Energy Distributions (SED) Significant energy output over wide frequency range “Big blue bump” (UV bump) – strongest energy output Infrared bump – energy output comparable to UV bump Important in determining the bolometric luminosity of quasars (AGNs) Quasar SED (Elvis et al. 1994) Infrared broad band photometry

Recent Results from Spitzer (broad band – IRAC) 259 SDSS quasars (Richards et al. 2006, astro-ph/ ) Overall SEDs consistent with the mean SEDs of Elvis et al SED diversity leads to large uncertainty in determining bolometric luminosity if assuming mean SED, e.g., L Bol =9λL λ (5100Å).

Recent Results from Spitzer (broad band – IRAC, MIPS) 13 high-redshift (z>4.5) quasars (Hines et al. 2006, ApJ, 641, L85) Consistent with SEDs of low- redshift quasars (Elvis et al. 1994) Our project Mid-IR SED from spectra (Spitzer IRS) Study emission features Add best data from other bands (e.g., X-ray) Improve bolometric correction

Sample and Data (UV-optical) Sample 1: 22 PG quasars (Laor et al. 1994, Shang et al. 2003) Sample 2: 17 AGNs from FUSE UV-bright sample (Kriss 2000, Shang et al. 2005) Z < 0.5 Quasi-simultaneous UV-optical spectra to reduce uncertainty from variability Rest wavelength coverage 1000 – 8000 Å, (some 900 – 9000 Å) FUSE HST ground-based

Sample and Data (Infrared) Sample 1: 22 PG quasars (Laor et al. 1994, Shang et al. 2003) Sample 2: 17 AGNs from FUSE UV-bright sample (Kriss 2000, Shang et al. 2005) Spitzer IRS mid-IR spectra (rest frame ~5-35 µm) MIPS far-IR (24, 70, 160 µm) photometry (not used) Available mid-IR spectra + UV-optical Total 15 objects (6 radio-loud, 9 radio-quiet) Silicates features at 10 and 18 µm (Siebenmorgen et al. 2005, Sturm et al. 2005, Hao et al. 2005, Weedman et al. 2005) Emission lines [Ne III ]15.56 µm, [O IV ]25.89 µm, …… Power-law between ~5-8 µm, and beyond

Results 1 of 3: Spectral Energy Distributions Our sub-sample of 15 objects: Composite spectrum (UV + optical + mid-IR) Normalized at 5600 Å Clear Silicates features around 10 and 18 µm

Results 1 of 3: Spectral Energy Distributions Our sub-sample of 15 objects: Composite spectrum (UV + optical + mid-IR) Normalized at 5600 Å Clear Silicates features around 10 and 18 µm Near-IR composite spectrum (Glikman et al. 2006) 27 AGNs (z<0.4) 1 micron inflexion

Result 1 of 3: Spectral Energy Distributions Our sub-sample of 15 objects: Composite spectrum (UV + optical + mid-IR) Normalized at 5600 Å Clear Silicates features around 10 and 18 µm Near-IR composite spectrum (Glikman et al. 2006) 27 AGNs (z<0.4) 1 micron inflexion Compared to the mean SEDs of Elvis et al Normalized to UV-optical Overall similar patterns More details with emission features

Result 1 of 3: Spectral Energy Distributions (diversity) Normalized at 5600 Å Normalized at 8 µm Individual mid-IR spectral are different. Contribute differently to the bolometric luminosity (L MIR ~8% to 30% of L Bol, assuming L Bol =9λL λ (5100Å) Bolometric luminosity estimate must take into account the diversity of the (mid-) infrared spectra. Mid-IR spectra can help to improve the bolometric correction.

Result 1 of 3: Spectral Energy Distributions (radio-loud/quiet) Normalized at 5600 Å Normalized at 8 µm Small difference between radio-loud and radio-quiet

Result 2 of 3: Evidence of Intrinsic Reddening

Result 2 of 3: Evidence of Intrinsic Reddening (Is it real?) Correlation holds without the “outliers”.

Result 2 of 3: Evidence of Intrinsic Reddening (is it real?) Correlation holds without the “outliers” Correlation is NOT caused by a correlation between spectral slope and the UV luminosity. Show direct evidence of intrinsic dust reddening. All quasars have intrinsic reddening (our sample is blue). Mid-IR + UV-optical info could lead to good estimate of intrinsic reddening.

Result 3 of 3: Eigenvector one (EV1) in Mid-IR Our sub-sample of 15 objects: Composite spectrum (UV + optical + mid-IR) Normalized at 5600 Å Clear Silicates features around 10 and 18 µm (Boroson & Green 1992) Strong anti-correlation between [OIII] and FeII emissions Involve many other UV-optical, soft X-ray parameters. May related to covering factor. May be driven by Eddington Accretion ratio L/L Edd.

Result 3 of 3: Eigenvector one (EV1) in Mid-IR (Boroson & Green 1992)

Result 3 of 3: Eigenvector one (EV1) in Mid-IR Equivalent width of Silicates 10µm seems also to be a parameter of EV1. Consistent with the picture of covering factor. r=0.64, p=1.0%

Summary We constructed the UV-optical and mid-IR composite spectra of low- redshift broad-line (type I) quasars from a sub-sample. Unlike borad-band SEDs, the composites show detailed mid-IR features. Mid-IR spectra needs to be considered in estimating a better bolometric luminosity. All quasars seem to have intrinsic dust reddening. Mid-IR and UV-optical information may be used to estimate the intrinsic reddening. Silicates 10µm feature is a parameter in the Eigenvector 1 relationships. This agrees with the UV-optical results.